Updated scope name for blade related snippets

Updated the scope for the blade related snippets to be triggered only in blade.php files.
This utilizes the scope name defined in the sublime blade plugin. 
https://github.com/Medalink/laravel-blade/tree/laravel3

The scope has been changed from 

```
<scope>source.php</scope>
```

To

```    
<scope>text.html.laravel-blade</scope>
```